Wings of Wrath by C. S. Freidman Book Two of the Magister Trilogy

Kamala, a peasant woman, has claimed the powerful sorcery of the Magisters as her own-the ability to draw on the power of the human soul without dying for it. But in her rise to power she finds herself hunted by the brotherhood, and flees to a land where spells are warped by a fatal curse. A land that even Magisters fear...